This invention relates to a system for X-Y pixel coordinate encoding, and more particularly to a system for treating the encoded array of an X-Y arrayed display system as containing a subpixel array, and weighting the value of the pixel display in accordance with the position of a display vector through the subpixel array to maximize the probability of entering the best data into a particular fixed location.
In many scanning systems for video display, such as in an ultrasound scanning system of the type disclosed in U.S. Pat. Nos. 3,864,660 and 3,864,661, the scanning vector may have virtually any angle with respect to an X-Y display coordinate. A scan converter stores the pixel values of the signal in a memory plane from which they are read out using the X-Y coordinates of the display system to address the memory plane.
It is sometimes desirable to use a digital memory to store the pixel values. This requires sampling the signal for each pixel of the vector, converting it to digital form, and storing it in the digital memory at a location specified by the X and Y coordinates of the pixel.
In the past, binary rate multipliers, or other similar devices, have been used to vary the sampling (pixel) clock rate in proportion to the sine or cosine of the vector angle. With such a system, correlation between the X-Y coordinates of the display system and the samples of the video signal along the scan vector is significantly less than 100% and allows for typical accuracy of only .+-.1/2 pixel. For example, a vector which just traverses the corner of a pixel, and goes through the core of another pixel, will produce equal pixel values for both the corner pixel and the core pixel, and everything in between. Any slight error in determining the location of the vector is further aggravated by this inability to distinguish between passing through the core of a pixel and barely passing through a corner or edge.